To contract charging times of respective batteries, by adopting a two-stage charging method using a provided rectifier with a large current capacity and a plurality of provided rectifiers with respective small current capacities, and by performing the chargings of the respective batteries by the rectifier with a large current capacity while switching the rectifier time-divisionally to the respective batteries.

Providing in a charger 2 a rectifier 5 with a large current capacity, rectifiers 9, 10, 11 with respective small current capacities, switchover circuits 6, 7, 8 and a charging sensor 12, first, a battery 13 is connected with the rectifier 5 by the switchover circuit 6 to perform a large-current charging. Then, when one of the voltage, temperature rise and gassing generation of the battery 13 or their composite value reaches a preset value, on the basis of the signal of the charging sensor 12, the connection of the battery 13 is switched from the rectifier 5 to the rectifier 9 by the switchover circuit 6 to connect simultaneously a battery 14 with the rectifier 5 by the switchover circuit 7. The switchovers performed when the state values of the batteries 14, 15 reach their respective preset values are executed by similar methods. Still, the chargings by the rectifiers 9, 10, 11 are completed respectively after respective preset lapses of time.